In accord with the literature, the process for preparing iminoethers as intermediate products may be described by the following general equation, starting with a corresponding nitrile: ##STR1## IN WHICH R represents an organic residue, such as, for example, a lower alkyl group; HO-alkyl stands for a lower alkanol and H-halide means hydrochloric or hydrobromic acid. As shown, the iminoethers are obtained in the form of salts. Very often this fact results in an undesirable precipitation during the batch reaction or the continuous process for preparing them. If this occurs, the manufacturing process is adversely affected because for completion of the reaction or for subsequent reactions, e.g., with ammonia, the reaction partners should be present in a homogeneous solution. Furthermore, the process of forming iminoethers is exothermic and must be accomplished by cooling. Crystallization of the salt, however, is an additional exothermic phenomenon which might occur within a very short period of time. In addition, an immediate overheating of the reaction mixture very often runs out of control.
Heretofore, 2-isopropyl-4-methyl-6-hydroxy pyrimidine was prepared by treating ethyliminoisobutyrate hydrochloride with ammonia to obtain the amidine of the formula ##STR2## and reacting the latter with methylacetoacetate. Ethyliminoisobutyrate hydrochloride has been manufactured according to the equation given at the outset starting with isobutyronitrile (IBN), hydrogen chloride (HCl) and ethanol. However, though it appeared highly desirable to replace ethanol by the less expensive methanol in the iminoether process inasmuch as the latter could simultaneously be used as solvent and more easily distilled off due to its lower boiling point, it had heretofore not been done because in practice it was found that methyliminoisobutyrate hydrochloride precipitated very readily during the reaction and under normal reaction conditions in the range of 15.degree. to 25.degree. C. about equimolar amounts of IBN, methanol and HCl led to crystallization of the final product during the reaction with all of the disadvantages as outlined above.